The main Wikipedia article says that the flag flown from a jack staff is an itty-bitty one called a "Jack" -- but that it's now common usage to use both "Union Jack" and "Union Flag" to refer to the full-up flag

Regarding Sir Mick: "While you're about it, perhaps you could also point out to him that "Get off of my cloud" (the chorus of the song) is not the kind of English that he was knighted for."
That is the sort of English up with which one should not put... ;)

And I was just getting over my North American ignorance of thinking that UK, Britain and England were one and the same ... oh well.
Flying a flag upside down is used as a universal call of distress, however the Union Flag/Jack does make it difficult due to its intricacies of design. I'll admit that I never knew about the spacing relationships of the diagonals, but now I should be able to tell ... thanks for the education

When I was a boy scout, back in the mists of time, we got taught about this but I'd forgotten it till I saw this. If you remember that the top red diagonal furthest from the flagpole has to be high in its white band, that works no matter which side you look at.
I remember pointing out to someone that their flag was upside down and getting roundly abused for my trouble....